I don’t expect you to recall our original blog on the concept of esophoria at near in convergence insufficiency, which dates back to January 28, 2015. From time to time, in the ensuing year and a half, I’ve had colleagues ask me where I wrote about that – so I know that the concept has been useful. I’ve been doing some “housekeeping” in the office lately, and came across a file I created about 20 years ago with the concept that one can measure orthophoria or even eso at near in some cases that can still be legitimately labeled as CI for coding purposes.
The first of three additional sources in addition to the ones I cited in the previous blog comes from the Journal of Pediatric Ophthalmology and Strabismus. The lead author is Sara Shipman – considered to be the premier orthoptist in New York City since I first set foot professionally in downtown Manhattan at SUNY-O in 1982, a mile or two up the road from her clinic at NY Eye & Ear. In convergence insufficiency with normal parameters, Shipman and colleagues write: “Pure convergence insufficiency is an anomaly of functional convergence without a significant heterophoria. Unlike Duane’s classification of convergence insufficiency as an exo deviation larger at near than distance, pure or functional convergence insufficiency are patients with asthenopic symptoms upon reading or near work not related to a significant hetreophoria, esophoria, or orthophoria.”
- Shipman S, Infantino J, Cimbol D, Cohen KR, Weseley AC. Convergence insufficiency with normal parameters. J Ped Ophthalmol Strab 1983;20(4):158-61.
The second source is a chapter in the Textbook of Ophthalmology, edited by Steven Podos and Myron Yanoff. Volume 5 of the Textbook, covering Strabismus and Pediatric Ophthalmology, is co-authored by Gary R. Diamond and Howard M. Eggers. In the chapter on Exotropia, regarding convergence insufficiency, it states: “Typically a small phoria occurs at distance and an exophoria or intermittent exotropia at near, although orthophoria or even esophoria also may occur at near. On rare occasions the effort to fuse may result in accommodative spasm.”
- Diamond GR, Eggers HM. Strabismus and Pediatric Ophthalmology: Exotropia. In SM Podos, M Yanoff eds. Vol. 5: Textbook of Ophthalmology. St. Louis: Mosby, 1993.
The third source is Martin Birnbaum’s textbook, Optometric Management of Nearpoint Vision Disorders. In reviewing models of nearpoint stress, Birnbaum notes that several clinical observations suggest a tendency toward overconvergence in patients with convergence insufficiency, particularly under fused conditions where eso fixation disparity and eso associated phorias are often demonstrated. Eso projection is often seen on cheiroscopic tracings and Van Orden Star patterns. Even under dissociated conditions, exophores frequently show an esophoric shift following brief periods of reading or upon repeated phoria measures. Since he views CI as an adaptive buffer to nearpoint stress and esophoria, it is not surprising that eso creeps in to clinical measures and profiles.
- Birnbaum MH. Optometric management of nearpoint vision disorders. Boston: Butterworth-Heinemann, 1993:60.